A method for operating a regenerative braking system of a vehicle and a control device for a regenerative braking system of a vehicle are described in German Patent Application No. DE 10 2012 211 278 A1. During an execution of method, at least one valve of a brake circuit of the regenerative braking system is activated before and/or during operation of a generator of the regenerative braking system in such a way that brake fluid is displaced via the at least partially open at least one valve from a master brake cylinder of the regenerative braking system and/or the at least one brake circuit into at least one storage volume. In this way, a brake pressure increase in at least one wheel brake cylinder of the braking system is to be able to be limited or prevented. Preferably, enough brake fluid is displaced into the at least one storage volume that solely regenerative braking is possible. The generator braking torque exerted with the aid of the generator is to correspond in this case to a setpoint total braking torque requested by the driver, while no hydraulic braking torque is exerted on an associated wheel with the aid of the at least one wheel brake cylinder.